1. Field of the Invention
The present invention relates to a technique of a double-sided printing in which a sheet that has been printed on one surface is reversed and the printing on the other surface thereof is performed.
2. Description of the Related Art
As double-sided printing systems of printing apparatuses, there is well known a system in which printing on one surface of one paper sheet and the printing on the other surface of the one paper sheet are continuously performed and then the printing on one surface of a paper sheet which follows the one paper sheet and the printing on the other surface of the paper sheet which follows the one paper sheet are continuously performed (hereinafter referred to as a double-sided continuous system). On the other hand, there is a printing apparatus which adopts the following system. That is, the printing on one surface of another paper sheet is performed during a time after the printing on one surface of one paper sheet is performed and before the printing on the other surface of the one paper sheet is performed, that is, the printing on one surface of one paper sheet and the printing on one surface of another paper sheet are continuously performed (hereinafter referred to as a single-sided continuous system). According to the single-sided continuous system, a length of time after the printing on one surface of one paper sheet is performed and before the printing on the other surface of the one paper sheet is performed (i.e. a time for reversing the paper sheet) can be allocated to the printing on another paper sheet. Therefore, in a case that the single-sided continuous system is adopted, it is possible to perform a printing process faster than a case in which the double-sided continuous printing system is adopted, in an amount of time corresponding to the time for reversing the paper sheet.
Here, conventionally, there is a printing apparatus which is aimed at improving the number of sheets to be subjected to the printing process (a throughput) per unit time with respect to a sheet having a short sheet-length unless a transport speed of the sheet is increased. It is noted that the sheet-length refers to a length of the sheet in the transport direction. The above printing apparatus is configured as follows. That is, in a case that the sheet to be used has the short sheet-length, a larger number of sheets are made to wait in a re-reversing route as compared with a case in which the sheet to be used has a long sheet-length.